Materials Science Forum Vol. 967

Abstract: Alkali activated slag (AAS) has gained huge attention in recent years due to its ability to replace ordinary Portland cement (OPC) as a binder in concrete. A need to replace OPC is imminent due to the high carbon dioxide emitted into the environment during its production. However, the use of this type of binder did not eliminate the huge strain placed on the deposit of natural resources. With the demand for concrete predicted to rise significantly in coming years, this means there will be a consequential increase in the amount of natural deposits of aggregates exploited, as aggregates make up about 80% by the volume of concrete. Therefore, in order to meet this forthcoming demand of sustainable concrete, and reduce the excessive strain on the use of natural aggregates, it is essential to find alternative materials that can be used as aggregate in concrete using AAS as a binder. This paper summarizes experimental results from various studies on the use of waste materials on aggregate. The fresh and hardened properties, alongside the cost and sustainability indications, are explored. It was drawn from this review that more reduction in carbon dioxide emission and cost could be achieved with the use of waste materials as aggregate in concrete. In addition, concrete made with AAS as a binder and incorporating waste as aggregate showed similar/higher properties with those made with natural aggregate. However, proper selection of types of wastes and replacement levels of these waste materials used as aggregate is still required to achieve enhanced properties.

Abstract: Different initiatives have evolved over the years to improve the durability of concrete, and one of the promising areas gaining attention in recent years is the use of nanomaterials in concrete. Though most of the applications of nanomaterials to improve the properties of concrete has been restricted to laboratory applications, it is anticipated that in few years to come more commercial and large-scale applications will ensue. This overview explored different types of nanomaterials already used in concrete and their effects on the durability of concrete. It was found out that nanosilica is the most used nanomaterial in concrete. And all types of nanomaterials currently used, enhance the durability of concrete significantly compared to other methods employed before the advent of nanomaterials in concrete. However, the use of other nanomaterials such as nanotitania and nanoalumina is attracting great attention. But the use of nanomaterials in concrete is faced by several challenges such as its high cost, production process, toxicity, etc. It is expected that with more research and application in the use of nanomaterials to enhance the properties of concrete, cheap and user-friendly nanomaterials can be developed. In addition, this review shows the possibility of enhancing the current durability properties with the use of nanomaterials.

Abstract: This study was conducted as a part of a research to assess the influence of the volumetric properties of geopolymer artificial aggregates made of fly ash to the performance of asphalt mixture to be used in pavement layers. This paper presents the parameters adopted during the production of geopolymer artificial aggregates which may affect the volumetric properties and the structure of the aggregates. The investigated volumetric properties included specific gravity and water absorption. In the experiment laboratory, two variables were utilized for producing the artificial aggregates, which might affect the considered volumetric properties. Those variables are pan-granulator slopes and alkaline ratios (the ratios of Sodium Silicate to Sodium Hydroxide). The pan-granulator slopes were set at 3 different angles, i.e. 45^o, 50^o, and 55^o. The selected alkaline ratios were 1.5, 2.0, 2.5, and 3.0. The test results indicated that the best volumetric properties were obtained at a slope of 50^o and alkaline ratio of 2.5. The bulk specific gravity values at the best volumetric properties were found to be: 1) oven dry at 1.9 grams/cm³; 2) saturated surface dry (SSD) at 2.0 grams/cm³, and 3) apparent at 2.1 grams/cm³ with 6% water absorption. In addition, the interfacial transition zone and microstructure aggregates were examined by using Scanning Electron Microscope (SEM). In this study, it was found that there were effects of Na₂SiO₃/ NaOH ratios and the granulation method on the volumetric properties.

Abstract: An exothermic chemical reaction between cement and water or is called as hydration of cement produced heat in which gives significance impact to the cement or concrete produced. This hydration of cement is similar to geopolymerization as in geopolymerization, heat is liberated when any pozzolanic material mixes with alkaline solution. Heat released for both hydration of cement and geopolymerization can be measured in a form of calorimetric data. This paper reviews on the use of heat released information for a better understanding on the reaction kinetics of geopolymerization and correlating the heat released with several factors including concentration of alkaline solution, mixing designation and curing temperature.

Abstract: Geopolymer system which has high demand, especially among carbon conscious end users resulted in various research works on suitable mix designs of geopolymeric materials. There are certain factors that influence the properties of geopolymers such as composition, type and relative amount of alkali activator, NaOH concentration, specific surface composition of source materials, and condition during the initial period of the geopolymerization process. Focus of our work is on the degree of influence NaOH concentration has towards mechanical and bonding properties of kaolin geopolymer coated lumber wood. Other crucial parameters were kept constant at optimum that was deduced based on our earlier findings. The final idea is to create kaolin based coating material that is compatible with wood substrates which leads to a novel finding. To best of our knowledge, no researchers had attempted to do similar work before. Kaolin geopolymer coated lumber wood was prepared with varying NaOH concentration ranging from 2M to 14M. These pepared samples were tested after 7, 28 and 90 days to also analyse the changes in properties of kaolin geopolymer coated lumber wood over time. Samples were then subjected to mechanical and bonding testings such as flexural, adhesive, and water absorption as well. Morphological studies such as scanning electron microscopy were also performed to further evident findings from all testings.

Abstract: Undershot waterwheels have been used by the people in rural areas to lift and distribute the water to the bottom which is higher than the water source. Waterwheels has a relatively simple design, large diameter, high speed and high torque. But applying it as a microhydro with high speed and small diameter still has to be explored. Waterwheels can operate efficiently in locations with high flow speeds. The Waterwheel functions from a waterwheel blade as a place to ride water so that the wheel can spin. From the results of the study, it can be concluded that the higher the flow of water with a large number of buckets, the speed of rotation of the wheel will be slower. Conversely, the lower the flow of water with the number of buckets a little then the spinning wheel is faster.

Abstract: This research is about nanoparticles hematite (NPH) synthesized and characterized from natural iron sands using co-precipitation method and its potential applications as extrinsic semiconductor materials type-N. The aims of this study is to determine the process parameters to obtain hematite of high purity degree and to observe its physical characteristics as an extrinsic semiconductor materials type-N. The iron sand was first separated by magnetic technique and then dissolved into HCl solution before conducting the precipitation process. Precipitation was done by dripping ammonium hydroxide (NH₄OH). Precipitated powder was dried at 80°C for 2 hours, and then calcined at 500°C, 600°C 700°C for 2 hours respectively. The composition of iron sands, purity degree, hematite mineral grain size, and space group were analyzed by XRF, XRD, FTIR and SEM. The XRF analysis result of raw material, showed that dominant element and composition in the sample is Fe with purity degree is 90.51%. The XRD result before and after precipitation showed Fe₃O₄ and α-Fe₂O₃. Fe₃O₄ purity degree was obtained 85%, and α-Fe₂O₃ in NPH500, NPH600, NPH700 were 63%, 83%, and 76%, respectively. FTIR spectral showed crystalline hematite characteristics stong band of 472.07 to 559.62 cm^-1. SEM image showed the morphology of agglomeration particulates, when the calcinaton temperature increases, the agglomeration will be seperated due to thermal energy. Based on the charaterization results it was found that the natural iron sand synthesized has the potential to be applied as an N-type extrinsic semiconductor material.

Abstract: The main objective of this study is to investigate the thermo-mechanical properties of composite made from geopolymer/carbon fiber/TiO₂ NPs. The composite was fabricated from geopolymer based on metakaolin added with carbon fibers as reinforcement and TiO₂ NPs as self-cleaning agent. The thermal properties of the composite was examined by subjecting the samples to temperature up to 750^OC for 4 hours. The mechanical properties of the resulting materials were measured by using flexural and tensile strength measurements. The experimental results showed that the compsite exhibited high temperature resistance and the addition of carbon fiber were increase the flexural as well as the tensile strength of the composite.

Abstract: The main objectives of this study is to investigate the properties of photoactive Nano TiO₂ thin film-geopolymer based on laterite soils deposit Gowa regency as self-cleaning material. The soil was clean, grounded, sieves 200 mesh and dehydroxylated at 750 for 2 hours. Nano TiO₂ was prepared through ball milling process for 10 hours. The geopolymers was synthesized through alkali activation method by adjusting the molar oxide ratios of SiO₂/(Al₂O₃+Fe₂O₃), Na₂O/SiO₂ and H₂O/Na₂O in accordance with the chemical compositions of the soils. Nano TiO₂ was added into geopolymers paste at different concentration namely 0.5% and 1.0% (relative to the mass of laterite soils) by using spray method. The self-cleaning properties of the sample were observed by immersing the sample into clays solution then irradiated under UV lamp for 24 hours. The X-Ray Diffraction (XRD) was performed to examine the structure and phase of the sample. The surface morphology of geopolymers was studied by using scanning electron microscopy (SEM). The measurements results showed that photoactive Nano TiO₂-geopolymers composite can be applied as self-cleaning materials.

Abstract: CuO nanoparticles (CuO-NPs) have been attracted much attention recently as a functional material. This study was conducted to investigate the properties of geopolymer-CuO-NPs as a functional composite. Geopolymer paste was produced through the alkali-activation method of metakaolin. CuO-NPs was synthesized from precipitation of CuSO₄ in NaOH solution. The composites were developed by mixing geopolymer with CuO-NPs varying the concentration of CuO-NPs relative to metakaolin. The structure of the raw materials, as well as the resulting composites, was examined by using x-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). The mechanical properties of the composites were measured by using compressive and flexural measurements. The measurements results showed that geopolymer CuO-NPs composites offer a wide range of potential structural applications.